The document discusses the simple past tense in English. The simple past is used to talk about completed events in the past, such as things that happened yesterday or last year. For positive sentences in the simple past, -ed is added to most verbs. However, for verbs ending in e, only -d is added, and for verbs ending in a consonant and y, the y is changed to i before adding -ed. Negative sentences in the simple past use the helping verb "did" followed by the base form of the main verb, or the contraction "didn't".